Acute cognitive effects of nonconvulsive difficult-to-detect epileptic seizures and epileptiform electroencephalographic discharges

This study compares the acute cognitive effects of short nonconvulsive seizures with the effects of interictal epileptiform electroencephalographic (EEG) discharges in children. The study is a prospective, standardized, nonrandomized, and open clinical comparative study. Eligible patients were included when they had (a) unclear seizures and fluctuations in cognitive performance and (b) frequent epileptiform EEG discharges in a recent EEG. All children were assessed with EEG/video (Brainlab) simultaneously with computerized neuropsychologic testing (FePsy) assessing motor speed/alertness, mental speed/attention, and memory function. Eleven patients with short nonconvulsive seizures during cognitive testing were included and compared with 11 matched patients with interictal epileptiform EEG discharges during cognitive testing but without seizures. Patients included in both groups had a reconfirmed diagnosis of epilepsy. Cognitive performance for both groups was compared. Statistical analysis showed significant correlations between the number of seizures (during cognitive testing) and impaired alertness and between the duration of the ictal period and memory impairment. Interictal epileptiform EEG discharges do not have an additional independent effect on cognitive function. The results demonstrate the accumulating cognitive effect of seizures and illustrate that frequent seizures, even when these are short in duration and with subtle symptomatology, can have a substantial impact on daily life and can lead to state-dependent learning impairment. Alertness and short-term memory appeared to be the functions that are most vulnerable for the acute effects of seizures.     

Relative influence of epileptic seizures and of epilepsy syndrome on cognitive function

Cognitive impairment is frequently observed in children with epilepsy. We aimed at addressing to what extent cognitive function is affected by paroxysmal epileptiform activity with or without clinical seizures or by clinical features characteristic of the epilepsy syndrome. To this purpose, combined electroencephalographic (EEG) recording and cognitive testing (IQ and reaction times) were performed in 28 children. Frequent epileptiform EEG discharges significantly reduced reaction time, as did the occurrence of seizures during cognitive testing. Syndrome-related factors tended to affect cognitive functions as well: children with generalized epilepsy and high average seizure frequency obtained lower scores. Linear regression analysis showed that stable aspects of cognitive function, as reflected in intelligence level, are most closely related to the severity of the epilepsy syndrome (average seizure frequency), whereas transient aspects of cognitive function, such as reaction times, are related to the occurrence of epileptiform EEG discharges. This suggests that seizures have a direct effect on transient cognitive aspects, which can accumulate and result in effects on intelligence level.     

Effects of epileptiform EEG discharges on cognitive function: is the concept of "transient cognitive impairment" still valid?

In this article we review the existing evidence on the cognitive impact of interictal epileptiform EEG discharges. Such cognitive impairment occurs exclusively in direct relation to episodes of epileptiform EEG discharges and must be distinguished from (post) ictal seizure effects and from the nonperiodic long-term "stable" interictal effects caused by the clinical syndrome or the underlying etiology. Especially in patients with short nonconvulsive seizures, characterized often by difficult-to-detect symptoms, the ictal or postictal effects may be overlooked and the resulting cognitive effects may be erroneously related to the epileptiform EEG discharges. The existing epidemiological data show that the prevalence of cognitive impairment during epileptiform EEG discharges is low. In one study 2.2% of the patients referred to a specialized epilepsy center for EEG recording showed a definite relationship between epileptiform EEG discharges and cognitive impairments ("transient cognitive impairment"). Several studies have sought to analyze to what extent cognitive impairment can be attributed to epileptiform EEG discharges among the other epilepsy factors (such as the effect of the clinical syndrome). These studies show that epileptiform EEG discharges have an additional and independent effect, but this effect is mild and limited to transient mechanistic cognitive processes (alertness, mental speed). This finding concurs with clinical studies that also reported only mild effects. In only exceptional cases are epileptiform EEG discharges the dominant factor explaining cognitive impairment. In addition, some studies have indicated that such mild effects may accumulate over time (when frequent epileptiform EEG discharges persist over years) and consequently result in effects on stable aspects of cognitive function such as educational achievement and intelligence. Hence, the clinical relevance is that early detection of cognitive effects of epileptiform EEG discharges and subsequent treatment may prevent a definite impact on cognitive and educational development. The disruptive effects of epileptiform EEG discharges on long-term potentiation, as established in animal experiments, may be one of the neurophysiological mechanisms underlying this accumulation. In conclusion the concept of "transient cognitive impairment" is still valid, but refinement of methodology has shown that a large proportion of presumed transient cognitive impairment can be attributed to subtle seizures, while interictal epileptic activity accounts for a much smaller part of the cognitive effects than previously thought. In particular cryptogenic partial epilepsies are associated with the risk of cognitive impairment. We hope that increased clinical awareness of this need for early detection will stimulate longitudinal and prospective research that eventually also will provide an answer to the questions of when and how epileptiform discharges that are not part of a seizure need to be treated.     

Effect of epilepsy, seizures and epileptiform EEG discharges on cognitive function

Patients with an established diagnosis of epilepsy were included in three groups on the basis of the absence (Group 2) or presence (Group 3) of epileptiform EEG discharges or subtle seizures (Group 4) during the cognitive assessment procedure. A separate age-matched non-epileptic control group (Group 1) was formed. Twenty-five patients were included in each of the four groups. Thus, a total of 100 patients were investigated. The patients were assessed with continuous 21-channel EEG and video-monitoring, combined with cognitive testing. The results show consistently lower performance on cognitive tests for Group 4, the group with subtle seizures. The difference with the control group was significant for the intelligence subtests and for the complex information processing test (p<0.05). No transient cognitive impairment was found. The results are discussed in the light of possible factors that may be responsible for the lower test-scores in the patients of Group 4: both the ictal effects of the seizures themselves, postictal effects and the effects of the epileptiform EEG discharges may have had an impact on cognitive performance. Finally the absence of evidence for transient cognitive impairment in a group with frequent epileptiform EEG discharges is discussed in detail.     

The relative influence of epileptic EEG discharges, short nonconvulsive seizures, and type of epilepsy on cognitive function

PURPOSE: This study addressed whether cognitive impairment in children with epilepsy is caused by disease-related stable factors, such as the type of epilepsy, or by acute effects of paroxysmal epileptic activity such as epileptic EEG discharges. We studied a nonselected group with short nonconvulsive seizures, as these seizures may elude detection and may therefore persist over a longer period. In this group, the diagnostic issue is to differentiate between the combined effects of several epilepsy-related factors on cognition. METHODS: All children were assessed with 32-channel EEG, synchronized with a computerized cognitive test system and a video-monitoring system. Recording time was 2 h. The primary inclusion criteria were unclear seizures and fluctuations in cognitive performance and/or frequent epileptic EEG discharges in a recent EEG. RESULTS: One hundred fifty-two patients met the inclusion criteria; 31 patients appeared not to have a diagnosis of epilepsy and were used as a nonepilepsy control group. Our results show that type of epilepsy has an impact on stable cognitive functions, such as educational achievement. Paroxysmal epileptic activity (acute effects of seizures and epileptic EEG discharges) affects primarily transient mechanistic cognitive processes (alertness, mental speed). CONCLUSIONS: These results suggest that the effects of paroxysmal epileptic activity on transient cognitive mechanisms may accumulate over time and consequently affect the more stable aspects of cognitive function such as educational achievement. The clinical relevance is that early detection of the cognitive impact of seizure-related activity and subsequent treatment may prevent its detrimental impact on cognitive and educational development.     

Predictors of nonconvulsive seizures among critically ill children

Purpose: Continuous electroencephalography (EEG) monitoring is a valuable tool for the detection of seizures among critically ill children, in particular when these seizures occur without clinical signs: termed nonconvulsive seizures. Continuous EEG monitoring is a limited resource in many centers. We sought to identify which critically ill children most frequently experience nonconvulsive seizures, and thus may particularly benefit from continuous EEG monitoring. Methods: Single‐center review was undertaken of consecutive diagnostic continuous EEG (cEEG) recordings performed in our pediatric and neonatal intensive care units (ICUs). We examined the indications for monitoring, the clinical characteristics of monitored patients, the occurrence and timing of seizures, and clinical and EEG characteristics associated with nonconvulsive seizures. Key Findings: One hundred twenty‐one patients underwent diagnostic continuous EEG monitoring, for a mean duration of 26 h. Seizures were detected in 32% of these patients, of which 90% experienced some nonconvulsive seizures, and 72% experienced exclusively nonconvulsive seizures. Patients with nonconvulsive seizures had significantly greater odds of having acute epilepsy, acute structural brain injury, prior in‐hospital convulsive seizures, and the presence of interictal epileptiform abnormalities on EEG. Significance: Seizures are common among critically ill children undergoing diagnostic cEEG monitoring. The great majority of these seizures are nonconvulsive, requiring EEG for their detection. Predictors of nonconvulsive seizures include acute epilepsy, acute structural brain injury, prior in‐hospital convulsive seizures, and interictal epileptiform abnormalities on EEG. These findings can help inform future allocation of limited cEEG monitoring resources to those patients at greatest risk for nonconvulsive seizures.     

Effect of Seizures and Epileptiform Discharges on Cognitive Function

Summary: Several relationships have been obtained between cognitive impairment and epilepsy-related or treatment-related factors. One of these factors is treatment-related: the central cognitive side effects of the antiepileptic drugs (AEDs). The second and third factors are disease-related factors, i.e., the effect of the seizures and underlying epileptiform discharges in the brain and the localization of the epileptogenic focus in specific areas of the brain. Although most cognitive problems have a multifactorial origin and often several factors combined are responsible for the "make-up" of a cognitive problem, we have attempted to isolate one factor: the effect of seizures and epileptiform EEG discharges on cognitive function. Several studies show the impact of ictal activity, but special attention is required for the postictal and interictal effects of epilepsy on cognitive functions. This may explain substantial cognitive impairments in children with subclinical epileptiform discharges or with infrequent subtle seizures.     

Acute effects of subclinical epileptiform EEG discharges on cognitive activation

In this prospective, open, clinical comparative study we analyzed impairments of cognitive activation occurring during, immediately before and immediately after epochs with epileptiform EEG discharges of 3 seconds or longer, in an attempt to establish whether cognitive slowing occurs in direct association with an epoch with epileptiform EEG discharges and whether cognitive impairments precede or follow such an epoch. All children were assessed with EEG/video (Brainlab) simultaneously with computerized neuropsychological testing (FePsy): a test for cognitive activation (simple visual and auditory reaction time measurement). Thirty-seven epochs with epileptiform EEG discharges without clinical signs of a seizure (subclinical epileptiform EEG discharges) were evaluated. The results showed a statistically significant and clinically relevant slowing (35% compared to the overall reaction time), occurring during the epoch with epileptiform EEG discharges (repeated measurement analysis of variance p = < .05; df = 3; F-value: 3.293). No statistically significant slowing was found for the periods 'post-discharge' or 'pre-discharge'. Type of discharge was important and effects on cognitive activation were found exclusively for generalized discharges. This effect was, however, also seen in the remaining period, outside the 'peri-discharge' periods and thus seemed to represent a more general effect of the type of epilepsy on cognitive activation. Our results show that the acute effect of short epileptiform EEG discharges (duration 4.14 sec; sd 1.38) may be impressive, causing impairment (slowing) of cognitive activation. This effect was limited to generalized discharges. This effect was not observed for focal discharges, even during longer periods with discharges. However, it is reassuring that this impact on cognitive activation is limited to the actual period in which the discharges occur and does not have 'post-discharge' effects. The risk of accumulating effects that may have longer-lasting repercussions on higher-order cognitive functions therefore seems to be negligible.     

Education and Epilepsy: Assessment and Remediation

Summary: Learning difficulties in children with epilepsy may be caused by brain damage and should be investigated. In many cases, however, seizures and/or electroencephalographic (EEG) findings are the only signs of pathology. Frequency and type of seizures may be determining factors that should, if necessary, be evaluated by long-term EEG monitoring, preferably during school performance or in conjunction with neuropsychological assessment. This may prove that subclinical epileptiform discharges in the EEG can adversely affect the child's performance. Secondary psychological problems in epilepsy patients, combined with side effects of antiepileptic drugs, may cause or heighten learning problems. Prophylactic control of seizures with one appropriate drug may alleviate learning problems. Computerized neuropsychological testing with simultaneous EEG recording may reveal the influence of epileptiform discharges on cognitive function and also help to evaluate the effects of antiepileptic drugs. Objective assessment of subclinical epileptiform activity makes it easier to treat the pathology identified by the EEG with optimal dosage of the most appropriate drug. A balance is required because epileptiform discharges and even occasional seizures may be less disabling than side effects from large doses of several drugs. Information to the school and the parents concerning the patient's abilities and limitations may be as important as seizure control. Specialized teaching should be started early, when necessary, with the patient integrated into a normal school if possible. However, good functioning in a special school is preferable to marginal functioning in a normal school.     

Does Physical Exercise Influence the Occurrence of Epileptiform EEG Discharges in Children?

Summary: Purpose: To determine if, and how, epileptiform EEG discharges in children were influenced by physical exercise.
Methods: Twenty-six children with intractable partial and generalized epilepsy exercised during video-telemetry recording, aiming at exhaustion after ∼10 min.
Results: During the exercise, epileptiform discharges decreased in 20 of 26 children (17 children had at least 25% reduction) and showed a rebound increase after the exercise (17 of 26 children) compared to baseline conditions. This exercise-induced reduction in epileptiform discharges reached statistical significance only in the 16 patients with localization-related epilepsy. Five patients showed an atypical EEG response to exercise with either unchanged or increased epileptiform activity while exercising. As compared to the other patients, these 5 children had experienced frequent clinical seizures during or immediately after exercise in their leisure time.
Conclusions: In the majority of the tested children, epileptiform EEG discharges decreased during exercise. "Exercise-EEG" may be a helpful diagnostic tool to identify patients who are disposed to have exercise-induced seizures.     

Educational underachievement in children with epilepsy: a model to predict the effects of epilepsy on educational achievement

In this study, we evaluated the impact on educational achievement of four characteristics of epilepsy individually and combined: epilepsy syndrome (type of epilepsy), seizure type, the frequency of epileptiform electroencephalographic (EEG) discharges, and the effect of antiepileptic treatment. Simultaneously, the effect on cognitive function and the relationship between educational underachievement and cognitive impairment were evaluated, focusing on memory, attention, speed of information processing, and intelligence level. This study was an open, controlled, parallel-group, nonrandomized clinical investigation. Eligible patients were selected when referred to our center for assessment of relationships between epilepsy and learning impairment in the years 1997 to 2001. Separately, children without neurologic deficit and without educational delay were assessed with the same tests as the children with epilepsy. This latter group is used in this study as a control group. One hundred seventy-six children with epilepsy and 113 controls were included. Gender distribution and age were comparable for the two groups. All children were in regular primary education. The children were assessed with a test battery consisting of tests for educational achievement, cognitive tests and tests for reaction time, and tests for memory and intelligence. Multivariate analysis of variance for tests of educational achievement showed a statistically significant effect for type of epilepsy (F = 4.386; P = .04), caused by the statistically lower scores for patients with localized epilepsy and symptomatic generalized epilepsy. For the reaction-time tests, a statistically significant effect for epileptiform EEG discharges (F = 3.165; P = .01) and treatment (F = 4.472; P = .001) on both vigilance tests was found, caused by patients with frequent epileptiform EEG discharges and polytherapy. Two-way interactions showed an interaction with type of epilepsy, with more patients with symptomatic generalized epilepsy having frequent epileptiform EEG discharges and polytherapy. For memory, none of the analyses showed statistically significant effects. For intelligence only for type of epilepsy, a statistically significant effect was found (F = 10.174; P = < .001). We propose a model with the type of epilepsy (epilepsy syndrome) as the dominant factor explaining educational underachievement in children with epilepsy. Such educational underachievement is most prominent for the localized and symptomatic generalized epilepsies, which suggests a dominant impact of underlying etiology (brain dysfunction or damage). These epilepsies are characterized specifically by a lower intelligence; hence, this could be the primary cognitive factor mediating between the type of epilepsy and educational underachievement. From the other factors, treatment (the use of polytherapy) and frequent epileptiform EEG discharges are associated with impaired vigilance, which could have an additional influence on educational achievement. These factors are, however, not independent of the type of epilepsy.     

Continuous EEG predictors of outcome in patients with altered sensorium

PurposeTo evaluate EEG predictors of outcome in patients with altered sensorium suspected to have seizure and to assess whether short term EEG is as effective as long term continuous EEG (cEEG) in predicting the outcome of patients with altered sensorium due to neurological causes.MethodsWe identified 99 consecutive critically ill patients with altered sensorium in whom nonconvulsive seizures were suspected. They underwent cEEG. Functional outcome was assessed with the modified Rankin Scale (mRS) at 4 weeks, discharge or death. We compared efficacy of short term EEG and long term continuous EEG in recording the abnormal patterns on EEG. Logistic regression analysis was performed to identify EEG findings associated with poor outcome, defined as mRS 4–6 (dead or moderately to severely disabled).ResultsPoor outcome was associated with nonconvulsive seizures (NCS), nonconvulsive status epilepticus (NCSE), periodic lateralized epileptiform discharges (PLEDS), PLEDS plus, generalized periodic epileptiform discharges (GPEDS) and abnormal EEG background. Short term EEG can detect seizure activity and other electrographic markers of poor outcome but the values are statistically insignificant.ConclusioncEEG monitoring provides independent prognostic information in patients with altered sensorium and suspected seizures. Unfavorable findings include nonconvulsive seizures, periodic epileptiform discharges and abnormal background. Short term EEG is ineffective in detecting seizures on EEG in patients with altered sensorium and should not be used as substitute for Long term EEG     

The effects of the everyday environment on epileptic activity in three mentally retarded individuals

Three mentally retarded epileptic subjects with frequent epileptiform EEG paroxysms were monitored with simultaneous radio-telemetered EEG and video recording while they were exposed to their everyday environmental conditions. These conditions included prompts and reinforcement for performing vocational training tasks, speech therapy, eating and drinking, and cues for resting, waiting, playing, exercising, and relaxing. Epileptiform EEG activity and the occurrence of clinical seizures varied as a function of the particular environmental conditions. Epileptiform EEG discharges were longer in duration, and clinical seizures were more frequent in all 3 subjects during conditions which produced inactive behavior than during conditions which produced active behavior. The modulation of epileptiform activity by everyday environmental conditions carries implications for (1) the optimum structuring of the environment for mentally retarded patients with frequent, subtle seizures, and (2) the analysis of the effects of epileptiform discharges on behavior.     

Electroencephalographic Parameters in Assessing the Cognitive Function of Children with Epilepsy

Summary: Many biological and psychological possibilities have to be considered when attempting to explain cognitive dysfunction in the individual child with epilepsy. Electroencephalographic (EEG) information, which may be particularly relevant in some children, has mainly been studied in relation to the possible direct effects of seizure discharges on learning and behavior. Such discharges can be divided into transient, brief or prolonged. Prolonged seizure discharges includes nonconvulsive status epilepticus during wakefulness and status epilepticus during slow-wave sleep. In addition to the influence of seizure discharges, preliminary findings suggest that some children with epilepsy might have a subtle disorder of arousal mechanisms in sleep, possibly associated with impaired daytime performance.     

Epileptiform EEG activities of the centromedian thalamic nuclei in patients with intractable partial motor, complex partial, and generalized seizures

Centromedian thalamic nuclei (CM) epileptiform EEG activities were recorded in patients with intractable partial motor, complex partial, and generalized seizures through implanted recording-stimulating electrodes, used for seizure control. CM epileptiform activities showed either little or no correlation to focal surface cortical and amygdaloid activities in patients with partial motor and complex partial seizures: CM paroxysmal discharges were correlated to focal epileptiform ictal activities only during the contraversive movements of partial motor and complex partial seizures. In contrast, CM epileptiform activities were consistently correlated to widespread surface cortical activities and clinical symptoms of fully developed nonconvulsive and convulsive tonic-clonic generalized seizures; i.e., unilateral CM double spike-wave complex discharges significantly preceded (p less than 0.001) the contralateral CM and bilateral surface cortical discharges and symptoms of nonconvulsive generalized seizures. Unilateral CM fast-slow-fast paroxysmal discharges significantly preceded (p less than 0.005) those of the contralateral CM and bilateral surface cortical regions and symptoms of the convulsive tonic-clonic generalized seizures. Individual spike-wave complexes from the frontal region preceded (p less than 0.001 and p less than 0.005) those at CM and other cortical regions during the nonconvulsive and clonic generalized attacks. No correlations between CM and cortical epileptiform activities were found, however, in the case of abortive, subclinical thalamocortical EEG discharges.     

Psychiatric and Behavioural Disorders in Children with Epilepsy (ILAE Task Force Report): Subtle behavioural and cognitive manifestations of epilepsy

A subtle behavioural or cognitive manifestation of epilepsy can be defined in two ways. First, epileptiform discharges not presenting as obvious seizures may nevertheless affect cognition and/or behaviour. Second, the actual seizures may be obvious but the way they affect cognition or behaviour may not be. There is a growing body of evidence indicating that the epileptiform discharges in benign epilepsy with centrotemporal spikes can affect behaviour and cognition. The focal discharges in other forms of epilepsy can also be associated with behavioural change. The Landau‐Kleffner syndrome, the CSWS syndrome, transitory cognitive impairment and transient epileptic amnesia provide further examples of cognitive and behavioural manifestations resulting from subtle manifestations of the epilepsy. Prompt, effective antiepileptic treatment with medication or surgery can improve behaviour and cognition in at least some cases.     

Electroencephalography in clinical epilepsy research

Electroencephalography (EEG) remains central to the investigation of epilepsy. This review discusses two clinical problems at the temporal extremes of neurophysiologic recording: evaluation of the clinical significance of individual spike discharges in benign epilepsy of childhood with centrotemporal spikes (BECTS), and prolonged (several days) continuous EEG monitoring in the ICU. BECTS is misdiagnosed often, and probably mis-treated often as well. Though the long-term outcome is usually excellent, it remains unclear whether the individual epileptiform discharges have a clinical effect. Answering this question is difficult, in part because of the natural evolution of the epilepsy and its different appearance depending on wakefulness or sleep state, and also due to substantial methodologic problems in measuring short and long-term cognitive effects. Continuous EEG (CEEG) recording has grown remarkably over the last 10 years. It has proved crucial in the diagnosis of nonconvulsive status epilepticus (NCSE), especially in the ICU, given the usual lack of obvious clinical signs of seizures in most of these patients, many of whom are critically ill. Much progress has been made in agreeing on terminology for the EEG findings, but diagnosis is still complicated. More efficient and reliable technology is being developed to help process the massive amount of data captured by CEEG and make it more useful (and in a timely fashion) clinically. Still, it is not completely clear which patients should be monitored, for how long, and what is the best role for CEEG in assessing and adjusting treatment once the diagnosis has been made. Investigators are using CEEG to study “seizure burden,” to help determine what are the long-term effects of nonconvulsive seizures and NCSE, and to help guide treatment and improve outcome.     

Beneficial effects of antiepileptic medication on absence seizures and cognitive functioning in children

In this prospective clinical study, the effects on cognitive functioning of absence seizures, epileptiform EEG discharges, and their abolishment by antiepileptic medication were evaluated in patients newly diagnosed with childhood absence epilepsy or juvenile absence epilepsy. Eleven children in the study group and ten age- and gender-matched controls with mild asthma underwent combined video/EEG and neurocognitive assessment (IQ, fine-motor fluency, attention, visual and spatial memory). The neuropsychological assessment was repeated after the introduction of antiepileptic medication. Ten children with absence epilepsy became clinically seizure free. The study group improved in attention, fine-motor fluency, and visual memory. The controls improved only in fine-motor and attention skills. Duration of generalized 3-Hz spike-wave discharges and clinical absence seizures was negatively correlated with performance on the visual memory task. Cessation of seizures induced by antiepileptic medication may support neurocognitive functioning in children.     

Attention deficit hyperactivity disorder in children with epilepsy

Attention deficit hyperactivity disorder (ADHD) is more frequent in children with epilepsy than in general pediatric population. Several factors may contribute to this comorbidity, including the underlying brain pathology, the chronic effects of seizures and of the epileptiform EEG discharges, and the effects of antiepileptic drugs. Symptoms of ADHD are more common in some specific types of epilepsies, such as frontal lobe epilepsy, childhood absence epilepsy and Rolandic epilepsy, and may antedate seizure onset in a significant proportion of cases. In epileptic children with symptoms of ADHD, treatment might become a challenge for child neurologists, who are forced to prescribe drugs combinations, to improve the long-term cognitive and behavioral prognosis. Treatment with psychotropic drugs can be initiated safely in most children with epilepsy and ADHD symptoms.     

Ring chromosome 20 epilepsy syndrome in children: electroclinical features

Ring chromosome 20 mosaicism is associated with dysmorphic features, mental retardation, and intractable seizures, including recurrent episodes of nonconvulsive status epilepticus. The authors' findings in four children, all without dysmorphic features, indicate that mental deterioration and frequent subtle nocturnal frontal lobe seizures, associated with a characteristic EEG pattern, represent prominent additional clinical features not previously described in this syndrome. This emphasizes the importance of full-night video-EEG in children with frontal lobe seizures and cognitive deterioration.